The present invention relates to a device for measuring the angular speed of rolling contact bearings.
The U.S. Pat. Nos. 5,575,568 and 5,969,518 relate to and make known a device for measuring the angular speed of rolling contact bearings which comprises a protective shield which is mounted onto the rolling contact bearing, a phonic wheel which is mounted under the protective shield, and a sensor, which is mounted onto a stud which is outside the rolling contact bearing and which is provided with an external frontal surface which faces towards the phonic wheel and a reading cell which is arranged in a position that is adjacent to the frontal surface itself.
Even though, in the U.S. Pat. No. 5,575,568, the sensor is mounted in such a way that the frontal surface and the protective shield form a gap in relation to each other, in the U.S. Pat. No. 5,969,518, the sensor is mounted with the frontal surface arranged in direct contact with the protective shield itself with the further advantage that the majority of the frontal surface is protected from the intrusion of foreign objects.
It should, however, be taken into consideration that in both the U.S.A. patents which have been cited above, the sensor is not mounted directly onto the rolling contact bearing but is mounted by means of positioning a stud between the rolling contact bearing and the sensor itself, or by means of a non-homogeneous chain inside which there are varying allowances, which means that it is particularly difficult to obtain a gap of the necessary size and that it is also difficult to ensure that the frontal surface is in direct contact with the protective shield other than under ideal conditions of assembly, or under conditions in which there are considerably reduced allowances to the absolute detriment of the relevant manufacturing costs.
Furthermore, in both the U.S.A. patents which have been cited above the protective shield must necessarily be made of non-ferromagnetic material so that its own characteristics do not impinge upon the readings carried out by the sensor and, also, it must present a somewhat reduced thickness in order to avoid weakening the signal emitted by the phonic wheel in correspondence with the frontal surface of the sensor. The necessity of making the protective shield out of a non-ferromagnetic material is not only detrimental to the above-mentioned manufacturing costs, but it also means that it is difficult to reduce the thickness of the protective shield itself without resorting to measures which would, once again, be rather expensive.
The aim of the present invention is to produce a device for measuring the angular speed of rolling contact bearings, which will ensure that it is possible to position the sensor as near as possible to the phonic wheel and will also ensure that it is possible to protect the phonic wheel itself from the intrusion of foreign objects and will also eliminate the above-mentioned disadvantages while rendering the manufacture of such devices as cost-effective as possible.
According to the present invention a device for measuring the angular speed of rolling contact bearings will be produced comprising a protective shield which is mounted onto the rolling contact bearing, a phonic wheel which is mounted under the protective shield, and a sensor, which is mounted onto a stud which is outside the rolling contact bearing and which is provided with an external frontal surface which faces the phonic wheel; the device is characterised by the fact that the protective shield is defined by a rigid wall, which is mounted onto a fixed race of the rolling contact bearing, and which is provided with at least one passing housing for housing the frontal surface of the sensor; the passing housing is isolated from the outside and is delimited by the part which faces towards the phonic wheel by a rubber membrane which is suitable for remaining in contact with the frontal surface of the sensor.